1. Field of the Invention
This invention relates to a mechanism for cooling the internal center of an internal combustion engine directly with air.
2. Description of the Prior Art
It is known to employ air cooling in an internal combustion engine, and air cooling is particularly employed frequently in the small-sized engine for generating less quantity of heat. As the engine is increased in size, water or oil cooling of a liquid-cooling type is mostly employed. However, the coolant is mostly water. Since the boiling point of the water has less difference from the ordinary temperature of the engine when operated, the coolant immediately arrives at the boiling point if the load is increased or the engine is rotated at high speed to feasibly cause an overheating phenomenon to occur in the engine. The other disadvantages of the liquid-cooling type are that its structure is complicated, sealing devices for preventing the liquid from leaking under temperature changes at approximately 100.degree. C. must be provided, and its maintenance is complicated due to management of the quality and components of the coolant.
A radiator is required to lower the temperature of the cooolant in the liquid-cooling type, where the heat is exchanged with air. Since the mean temperature of the atmospheric air is approximately 20.degree. C. and approximately 50.degree. C. under the most severe conditions, there is sufficient temperature difference between the air and the boiling point of the coolant in the liquid-cooling type, and water is almost inexhaustibly available.